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Drones have come down in price and are increasingly popular with hobbyists

It was a hot and humid day when a shark alarm rang out across Australia's most famous beach, scaring swimmers out of the water at Bondi, Sydney.

The shark sightings came three days after a police helicopter spotted a bull shark in the Bondi surf in early January.

Helicopters are regularly used by surf life-saving associations to spot sharks at popular swimming beaches.

And the Bondi shark alerts - sounded when the beach was crowded with locals and tourists - have added impetus to the local council's decision to trial drones to help spot sharks.

Waverley Council has already conducted a test flight of one of these multi-rotor copters with an attached Go-Pro camera. It is now considering the legal and safety implications of the so-called spy-in-the-sky technology.

This is just one of a growing number of applications for the new technology.

Unmanned aerial vehicles (UAVs), as they are formally known, are frequently used for surveillance in war zones and by emergency services but also increasingly by the media, in land surveys, and in real estate and agriculture.

Governments around the world are turning their attention to how to regulate their use.

Australia was one of the first countries to introduce licences for commercial drone operators and regulations for both recreational and commercial use, in 2002.

Proposed changes to those regulations could soon make them among the world's toughest.

Close calls

According to Australia's Civil Aviation and Safety Authority (Casa), the number of businesses applying for a drone licence has risen sharply in recent years, from about 14 in 2012 to 180 licences today.

But it is impossible to gauge how many drones are being used recreationally, according to Casa's Corporate Communication Manager Peter Gibson, because "they can be flown straight out of the box without a licence".

Their popularity has also increased as prices have fallen from thousands of dollars to about A$500 ($404, £267).

Europe and the US have been slow to regulate drone technology and debate has stalled over how to protect people's privacy without stifling commercial uses. Other countries, such as Spain, have banned commercial drones altogether.

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The drone industry is rapidly developing new uses for the technology

Drones can be dangerous in the hands of amateurs, as a YouTube sub-genre devoted to drone crashes attests. Ensuring hobbyists abide by Casa rules is vital, says Mr Gibson.

The authority's pre-Christmas publicity campaign highlighted rules stipulating drones must be flown below 121m (400ft) and only in daylight, with the craft in sight at all times. Drones should not go within 5.5km (3.4 miles) of airports and must be no closer than 30m (98ft 5in) to people, vehicles and buildings.

But breaches inevitably occur. Last December, during a police siege at a house in Melbourne, a local man used a drone to film the siege. It crashed into a power line, narrowly missing a police officer. The owner was subsequently prosecuted and fined A$850.

More alarming is the number of times drones have been reported flying uncomfortably close to commercial jets. Over the past year in Australia, pilots reported seeing a drone close to their aircraft on 14 occasions.

In the US, there were 25 near-misses between drones and larger aircraft over a six-month period last year, according to the Washington Post.

It is vital that regulations be updated and that authorities try to anticipate new uses for drones, says Mr Gibson from Casa.

Risk to privacy

Media organisations are among the groups that have adopted the technology. Casa's rule changes are expected to make it easier for the media to use small drones.

Mark Corcoran, a seasoned international correspondent at the Australian Broadcasting Corporation (ABC), heads a project examining the pros and cons of using drones for newsgathering.

His interest in "drone journalism" began in 2006 when he was covering the conflict in Beirut and saw an Israeli military drone with a camera flying overhead.

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Regulators are likely to weigh the benefits of using drones against the risks

"This technology is a wonderful tool for seeing what's around the corner or over the hill when there may be a threat to your safety," says Mr Corcoran.

But drones can easily invade privacy and breach security. Last year, a Victorian real estate agent who was using a drone legitimately - to take aerial shots of a property - published photos revealing the neighbour sunbathing topless.

In France, drones have filmed nuclear power plants.

There have been calls for privacy protection governing drones to be enshrined in Australian law.

However, Mr Corcoran says governments may not want to over-regulate an emerging technology that has many positive, peaceful uses.

The public's attitude to drones will ultimately depend on what they can do and how they are used, he says.

"If a drone is used to save a surfer or swimmer, then it's all good," he says. "If an out-of-control drone is sucked into the engine of an airliner, it may well result in drone-control becoming highly contentious."